Abstract
Photosensitivity is defined by the occurrence of spikes or spikes and waves in response
to intermittent light stimulation (= photoparoxysmal response [PPR]). The EEG pattern
can show a wide range of expression from solely occipital spikes to generalized irregular
spikes and waves. The different types of responses represent different levels of expression
of the same genetically determined trait. The photoconvulsive response of Bickford
et al (7) is only a subtype of the PPR characterized by close relation to epilepsy.
The average incidence of PPR is 7.6 % in healthy children aged 1 to 16 years. Girls
are more often affected than boys.
The available data provide evidence for autosomal dominant inheritance of photosensitivity.
Genetic heterogeneity must be considered.
In studies starting from a neurobiological genetic point of view including the whole
spectrum of PPR, the phenomenon could be shown to be a widespread condition being
only loosely associated with epilepsy, but more often with symptoms of psychovegetative
instability. Only about 3 % of children with PPR of the given definition will manifest
epilepsy up to age 20 years. According to family studies in epileptic and non-epileptic
photosensitive probands, the phenotypical expression of the PPR and carriers' risk
to manifest epileptic phenomena is decisively determined by other pathogenetic factors
related to epilepsy. Possible interactions of photosensitivity within the multifactorial
pathogenetic background of the epilepsies are reviewed.
Key words
Photosensitivity - Genetics - Epilepsy
